1. Field of the Invention
The invention relates to press sections and methods of using the same for drainage of fibrous material webs, and more specifically to press sections with at least two nips.
2. Discussion of Background Information
DE 295 18 748 A1 describes a press section that includes two nips, which are each formed by a shoe press roll in combination with a smooth roll. The paper web is transferred from the wire section of the paper making machine onto an endless, smooth, and flexible pressing belt, which travels together with the paper web through the first nip and transfers the paper web onto the smooth roll of the second nip. In this press section, the guidance of the paper web through the last nip, and in particular after it, causes problems.
Accordingly, the present invention is directed to a method and device for a press section that substantially obviates one or more of the problems arising from the limitations and disadvantages of the related art.
It is an aspect of the present invention to provide a press section that assures an improved guidance of the fibrous material web, in particular after the last nip. It is another aspect of the present invention to provide a press section with improved drainage capacity, in particular in the last nip.
Accordingly, one aspect of the present invention is directed to a press section for drainage of a fibrous material web that includes a shoe press roll, a cylindrical counter roll, at least one nip, and a first nip of the at least one nip formed by the shoe press roll and the cylindrical counter roll, and at least one press felt. The at least one press felt is disposed on each side of the fibrous material web. The at least one press felt travels through a last nip of the at least one nip, after which the at least one press felt is separated from the fibrous material web and conveyed away after leaving the last nip.
According to another aspect of the present invention, the fibrous material web travels on the shortest possible path to a second cylindrical counter roll of the last nip after winding part way around the cylindrical counter roll of the first nip. According to yet another aspect of the present invention, the fibrous material web includes a paper web.
In a further aspect of the present invention, the at least one press felt is separated from the fibrous material web by a suction element. According to another aspect of the present invention, the at least one press felt is separated from the fibrous material web by a blower element. According to yet another aspect of the present invention, the one at least one press felt disposed on each side of the fibrous material web also travels through the first nip. In a further aspect of the present invention, the one at least one press felt disposed on each side of the fibrous material web travels through all of the at least one nips.
In still another aspect of the present invention, the at least one press felt travels through all of the at least one nips. According to yet another aspect of the present invention, the cylindrical counter roll of the first nip and the second cylindrical counter roll of the last nip are pressed at least slightly against each other. According to a further aspect of the present invention, the last nip is formed by the second cylindrical counter roll and a second shoe press roll. In another aspect of the present invention, the at least one press felt that carries the fibrous material web after leaving the last nip is conveyed past a suction element.
In accordance with yet another aspect of the present invention, the suction element includes a suction roll. According to a further aspect of the present invention, the suction element includes a suction box. According to another aspect of the present invention, the at least one press felt separated from the fibrous material web and conveyed away after leaving the last nip is conveyed past a blower element. In yet another aspect of the present invention, the blower element includes a blow box.
According to a further aspect of the present invention, the invention includes a method for drainage of a fibrous material that includes: forming a first nip between a first shoe press roll and a first cylindrical roll; forming a second nip between a second shoe press roll and a second cylindrical roll; forming a third nip between the first cylindrical roll and the second cylindrical roll; placing at least one press felt on each side of a fibrous material web; passing the fibrous material web with the at least one press felt on each side through at least one of the first nip, the second nip, and the third nip; separating the press felt from the fibrous material web after the fibrous web material passes through at least one of the first nip, the second nip, and the third nip; and conveying away the at least one press felt separated from the fibrous material web, wherein the drainage capacity and the reliable guidance of the fibrous material web are improved.
In another aspect of the present invention, the third nip is formed by slightly pressing together the first cylindrical roll and the second cylindrical roll. In yet another aspect of the present invention, the separating includes sucking the at least one press felt from the fibrous material web. According to a further aspect of the present invention, the separating includes blowing the at least one press felt from the fibrous material web.
According to still another aspect of the present invention, the at least one press felt passes through only the first nip. In yet another aspect of the present invention, the at least one press felt passes through only the first nip and the second nip. According to a further aspect of the present invention, the at least one press felt passes through the first nip, the second nip, and the third nip.
According to another aspect of the present invention, a press section for drainage of a fibrous material web is provided. The press section includes a first and second shoe press roll; a first and second cylindrical counter roll; a plurality of nips comprising, a first nip formed by the first shoe press roll and the first cylindrical counter roll, a second nip formed by the second shoe press roll and the second cylindrical counter roll, and a third nip between the first cylindrical roll and the second cylindrical roll; and at least two press felts, in which at least one press felt is disposed on each side of the fibrous material web, the at least two press felts being arranged to travel through at least one of the first, second, and third nips. Furthermore, the fibrous material web is always in contact with at least one of the at least one two press felts as it is guided from a first one of the first, second, and third nips to a last one of the first, second, and third nips; the at least one press felt on one side of the fibrous material web is separated from the fibrous material web after the fibrous web material passes through the last one of the first, second, and third nips; and the at least one press felt separated from the one side of the fibrous material web is conveyed away.
Other exemplary embodiments and advantages of the present invention may be ascertained by reviewing the present disclosure and the accompanying drawings.